Not thinking of one single thing, but there’s plenty of ways fingerprinting different users is likely possible. If you have 10K withdraws per user you can probably cluster the blinded paths many of them are using, add on top features which may identify specific clients and you can probably do pretty well. Obv you can’t tell the difference been any two invoices for different Phoenix (or other wallet with a fixed LSP (set)) wallets, but across wallets I’m skeptical it’s robustly private.